The invention relates to a method for monitoring the condition of a continuous element moving in a fiber web or paper finishing machine, said monitoring being performed with a rotating machine element, which is equipped with a sensor assembly that measures force or pressure and against which the continuous element moves, and wherein                the machine element is made to rotate against the continuous element,        a measurement signal is generated between the machine element and the continuous element with the sensor assembly,        a cross-directional profile of force or pressure generated between the machine element and the continuous element is formed from the measurement signal.The invention also relates to a corresponding system and a computer program product.        
Profiles, quality and/or tightness of parent rolls produced by paper machines and paper finishing processes have conventionally been monitored with manual methods. One of these is the knocking of parent rolls between reel rails during the operation of the machine. In this case, the user of the measuring device (wooden block or “Beloit Hammer”) goes in front of a rotating winding-up parent roll to perform the measurement. The user walks in the cross direction of the machine from side to side scanning, by knocking, the variations in the tightness and/or hardness of the parent roll and the quality of the roll in general. Based on the observations, conclusions are drawn regarding paper profiles, needs of profiling changes and modification needs of reel parameters (such as linear load).
Recently, safety at work has increasingly come to the fore in all aspects related to operating of paper machines. One manifestation of this is the attempt to prevent operators from going inside a paper machine, near rotating rolls, for example. For this objective, safety gates and light curtains are installed, for example. These ensure that one cannot access dangerous places during the machine operation. In new machines, such safety fittings are already standard equipment, particularly at reels and winders. In old machines, they will become more and more common as the machines are rebuilt. In western countries, user safety must be taken into account in each machine rebuild, and everything must be done to maximize safety. In practice, this leads to the necessity of denying user access to dangerous places.
Due to the aforementioned reasons, it is impossible for operators in many machines to gain access to profile monitoring in the wind-up section, which is an essential part of machine monitoring. This is because access between the reel rails is forbidden during the machine operation. This prohibition is further strengthened by equipping the reel with safety gates. Opening the door of the gates stops the production. The introduction of these safety improvements is grounded, since, when a web break occurs, an operator knocking a roll is in danger. This also applies to situations in which a parent roll starts to decompose for some reason. In such a situation, an operator feeling the surface of a parent roll will certainly get hurt and the risk of death is significant.
In addition to the knocking performed in an operating machine, it is of course also possible to try to monitor roll profiles by measuring, knocking and/or manually probing parent rolls that have already been completed and stopped. In this case, it is already late for any improving actions, as the roll is already completed. At this stage, nothing can any longer be done to improve its tightness or other properties. Furthermore, the measuring of even stopped parent rolls begins to be challenging today for safety reasons. In addition, it is difficult to enter the winder's unwinder or the preceding reel spool storage rails because of safety gates, for example. In some cases, the same applies even to shipping roll sets completed at the winder. In some mills (particularly in North America), access to the dry end side of the winder is also restricted.
In addition to the aforementioned rolls, manual methods have traditionally also been used to monitor paper machine fabrics. One example of these is the measurement of fabric tension with a manually operated tension measurement device. In this case, the user of the measurement device goes to a suitable position in a fabric run, close to the fabric, and presses the device against the fabric. The user walks in the cross direction of the machine from side to side scanning in this way variations in the fabric tension in the cross direction. Based on the measurement, it is possible to draw conclusions about the fabric condition, possible slackened areas and the future fabric change requirement. The condition of a fabric can also be monitored during the machine operation with moisture or permeability measurements.
Fabric and web tension measurement with a roll equipped with sensors is known from FI patent 113804. However, this publication does not propose a method for condition monitoring of a target element; instead, monitoring of both the fabric condition/wear and the roll quality/hardness have practically been implemented with the aforementioned manual methods.
For the aforementioned reasons alone, many mills have started to look for possibilities to get rid of fabric scanning and other inspections related to their condition performed during the machine operation, due to safety at work aspects. This poses a problem to operators, since it should be possible to monitor fabric wear even under conditions other than during a shutdown.